This invention relates, in general, to airbag systems, and more particularly, to squib ignitor circuits for airbag systems.
Besides the physical structure of an automobile, airbags and seat belts are the primary safety mechanisms in preventing injuries to an occupant in the event of an automobile accident. An airbag is a safety device that is deployed to cushion an occupant from an impact. Sensors in an automobile detect rapid deceleration or an impact via proximity sensors. Once an accident situation is detected, the airbags of a vehicle are deployed to prevent the occupants from hitting a hard surface within the automobile thereby preventing serious injury.
In general, airbags are placed in locations or surfaces of an automobile that previously caused occupant injuries. For example, head impact is prevented by placing airbags in the steering wheel or dash board of an automobile. Airbags are also placed in doors for occupant protection in side impacts and under the dash to prevent leg injuries.
The duration of a crash typically can be measured in milliseconds. The accident must be sensed and the airbag deployed within a few milliseconds after impact. Circuitry couples energy to a squib which is in contact with ignitor pyrotechnic material. The ignitor pyrotechnic material resides near the airbag inflator pyrotechnic material. Upon sensing an accident condition, energy is coupled to the squib which produces heat sufficient to ignite the ignitor pyrotechnic material. The hot gases produced by the ignition of ignitor pyrotechnic material ignites the airbag inflator pyrotechnic material. The burning inflator pyrotechnic material produces hot gases which expand into the airbag to inflate the airbag. The inflated bag cushions a person being propelled into the airbag during a collision.
A problem with airbags is the force at which an air bag is propelled from its enclosure when deployed. A person can be seriously injured by the impact of an inflating airbag. Airbag circuits have been designed to prevent inadvertent airbag deployment. Still, a wire of the airbag system shorted to a power source of an automobile can accidentally deploy an airbag. Rescue workers have needlessly been hurt trying to cut victims of an accident from an automobile when an airbag was deployed during the rescue attempt.
It would be of great benefit if a squib ignitor circuit could be provided that significantly reduces inadvertent deployment of an airbag.